Reference timing signal apparatus and method
First Claim
1. A reference timing signal apparatus for providing a timing output signal, the reference timing signal apparatus comprising:
- an oscillator for generating an oscillation output signal in response to a control component of an input control signal;
a difference detector for detecting a difference corresponding to a time difference between the oscillation output signal and an input reference timing signal when the input reference timing signal is available, thereby providing a difference signal;
an error calculator for calculating cumulative time error (CTE) in the difference signal over a given time period to provide a correction signal having correction data corresponding to the calculated CTE;
a processor for providing a frequency control value in accordance with the correction data and a frequency dependent element relating to the oscillator, the frequency dependent element being provided in accordance with a characteristic model that is updateable in accordance with the correction data when the input reference timing signal is available; and
an oscillation controller for controlling the control component of the input control signal applied to the oscillator in accordance with the correction data provided by the error calculator and the frequency control value provided by the processor.
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Abstract
A reference timing signal apparatus with a phase-locked loop (PLL) has a computer algorithm which adaptively models the multiple frequencies of an oscillator following a training period. The oscillator is part of a PLL and the oscillation frequency thereof is controlled in response to the phase detector output. The computer algorithm processes the control signal applied to the oscillator. The computer algorithm updates the characteristics of the model relating to the aging and temperature of the oscillator, using for example, a Kalman filter as an adaptive filter, in accordance with a cumulative phase error in the PLL calculated during a given time interval. By the algorithm, the subsequent model predicts the future frequency state of the oscillator on which it was trained. The predicted frequency of the model functions as a reference to correct the frequency of the oscillator in the event that no input reference timing signal is available. Also, the calculated phase error is stored and is used while no input reference timing signal or accurate predicted frequency value is available. With the model updating algorithm, oscillators of low stability performance may be used as cellular base station reference oscillator, which is based on satellite systems, for example, GPS, GLONASS or Galileo systems.
55 Citations
40 Claims
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1. A reference timing signal apparatus for providing a timing output signal, the reference timing signal apparatus comprising:
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an oscillator for generating an oscillation output signal in response to a control component of an input control signal; a difference detector for detecting a difference corresponding to a time difference between the oscillation output signal and an input reference timing signal when the input reference timing signal is available, thereby providing a difference signal; an error calculator for calculating cumulative time error (CTE) in the difference signal over a given time period to provide a correction signal having correction data corresponding to the calculated CTE; a processor for providing a frequency control value in accordance with the correction data and a frequency dependent element relating to the oscillator, the frequency dependent element being provided in accordance with a characteristic model that is updateable in accordance with the correction data when the input reference timing signal is available; and an oscillation controller for controlling the control component of the input control signal applied to the oscillator in accordance with the correction data provided by the error calculator and the frequency control value provided by the processor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. A method for providing a timing output signal, comprising the steps of:
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generating an oscillation output signal in response to a control component of an input control signal; detecting a difference corresponding to a time difference between the oscillation output signal and an input reference timing signal when the input reference timing signal is available; calculating phase error in a detected difference over a given time period to provide a calculated phase error; changing the control component of the input control signal in accordance with the calculated phase error and a frequency dependent element relating to the oscillator; providing the frequency dependent element in accordance with a characteristic model that is updateable in accordance with the calculated phase error when the input reference timing signal is available, wherein a frequency of the oscillation output signal generated by the oscillator is controlled in accordance with the control component of the input control signal, the timing output signal being provided in accordance with the oscillation output signal, whereby the timing output signal is provided when the input reference timing signal is unavailable. - View Dependent Claims (28, 29, 30, 31, 32, 33)
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34. An apparatus for generating a reference signal for use in a cellular base station, the apparatus comprising:
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a receiver for generating an input reference timing signal when a cellular signal is available; an oscillator for generating an oscillation output signal in response to a control component of an input control signal; a difference detector for detecting a difference corresponding to a time difference between the oscillation output signal and the input reference timing signal when the input reference timing signal is available, thereby providing a difference signal; an error calculator for calculating phase error in the difference signal over a given time period to provide a calculated phase error; a processor for providing a frequency control value in accordance with the calculated phase error and a frequency dependent element relating to the oscillator, the frequency dependent element being provided in accordance with a characteristic model that is updateable in accordance with the calculated phase error when the input reference timing signal is available; and an oscillation controller for controlling the control component of the input control signal applied to the oscillator in accordance with the calculated phase error provided by the error calculator and the frequency control value provided by the processor. - View Dependent Claims (35, 36, 37, 38, 39, 40)
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Specification